K321 won’t rev up

Restoring a k321 and the engine won’t rev up at all. Fresh rebuild new piston rings bored cylinder ground crank new points governor. Seems like it idles ok, I first started it a Walbro carb and idled perfect then, now not so much with the Chinese aftermarket. Tried adjusting jets but makes no difference. Was gonna try putting the walbro back on but I lost one of the jets but should be able to find it. The new fuel pump I found does not work but I have hooked up gravity feed from aux fuel tank. Walbro carb leaks when hooked up to Old fuel pump (I replaced fuel pump and I think I need to purge air out to make work) cleaned Chinese carb twice it had black crap inside before it wouldn’t run at all. Even before I rebuilt it would never rev up unless it got starting fluid. When it does rev, it spits and sputters and blows back out but I set valve lash right but will recheck that. So I’m thinking my issue is maybe a spark issue? I have a m14 engine I can rob the carb off that engine runs flawless so if carb is bad we can figure that out but I’m not sure that’s the case. Will try the Walbro since it worked before. Any help is very appreciated and will update as I find stuff

because you say it both won't rev up and it also blows back out of the carb., I wonder if you got the cam timed properly to the crank. There are two timing marks on the crank, one for the cam, one for the counterweights.

Another thought is the governor adjustment. the relationship between the arm with the throttle link and the shaft may have to be changed in order for the flyweights to work the throttle shaft on the carburetor as they have a somewhat limited travel.

Its also not unheard of for the governor gear to fall off its little shaft before everything is hooked back up.

I also remember one engine rebuild that wouldn't rev. and I finally noticed there was no condenser on the new coil. I am still surprised it would run at all.

Timing was lined up it was the crappy carburetor I got from eBay. Works now